Variable geometry turbine

Abstract

A variable geometry turbine includes a fluid space formed by a nozzle mount and a nozzle plate; and a plurality of nozzle vanes arranged in the fluid space at certain intervals in the circumferential direction so as to partition the fluid space. The nozzle vanes are supported by shafts on the nozzle mount, in such a manner as to be capable of turning. The flow rate of the discharged fluid can be adjusted by opening or closing the cross-sectional area of a flow path formed by the adjacent nozzle vanes. The nozzle plate is provided with plate projections protruding toward the nozzle vanes further than, at least, end surfaces of the nozzle vanes, so as to cover the spaces between leading edges of the nozzle vanes and trailing edges of the nozzle vanes adjacent thereto, when the nozzle vanes are at a closed position.

The invention claimed is: 
     
       1. A variable geometry turbine comprising:
 a fluid space that is formed in a donut shape by a pair of ring-like opposing surfaces arranged to face each other with a certain distance therebetween and that allows fluid flowing from an outer circumferential side to be discharged toward an inner circumferential side; and 
 a plurality of nozzle vanes arranged in the fluid space at certain intervals in a circumferential direction so as to partition the fluid space, the nozzle vanes being supported by shafts on one of the opposing surfaces in such a manner as to be capable of turning; 
 wherein the nozzle vanes are made to turn on the shafts to open or close throat spaces formed by adjacent nozzle vanes, so that the flow rate of the fluid can be adjusted, 
 at least one of the pair of opposing surfaces is provided with projections protruding toward the nozzle vanes further than, at least, end surfaces of the nozzle vanes so that the throat spaces formed between leading edges of the nozzle vanes and trailing edges of the nozzle vanes adjacent thereto have a reduced height in a direction along the shafts when the nozzle vanes are at a closed position, and 
 the projections are provided so as to entirely cover the throat spaces between the leading edges of the nozzle vanes and the trailing edges of the nozzle vanes adjacent thereto when the nozzle vanes are at the closed position. 
 
     
     
       2. The variable geometry turbine according to  claim 1 , wherein a tapered outer-circumferential surface, which is tapered toward each of the projections so as to approach each of the nozzle vanes, is provided on an outer circumferential side of the each of the projections. 
     
     
       3. The variable geometry turbine according to  claim 2 , wherein a tapered inner-circumferential surface, which is tapered toward the each of the projections so as to approach the each of the nozzle vanes, is provided on an inner circumferential side of the each of the projections. 
     
     
       4. The variable geometry turbine according  claim 3 , wherein the projections cover portions from the leading edges or the trailing edges of the nozzle vanes to positions adjacent to the shafts, in a chord direction of the nozzle vanes. 
     
     
       5. The variable geometry turbine according  claim 2 , wherein the projections cover portions from the leading edges or the trailing edges of the nozzle vanes to positions adjacent to the shafts, in a chord direction of the nozzle vanes. 
     
     
       6. The variable geometry turbine according to  claim 1 , wherein a tapered inner-circumferential surface, which is tapered toward each of the projections so as to approach each of the nozzle vanes, is provided on an inner circumferential side of the each of the projections. 
     
     
       7. The variable geometry turbine according  claim 6 , wherein the projections cover portions from the leading edges or the trailing edges of the nozzle vanes to positions adjacent to the shafts, in a chord direction of the nozzle vanes. 
     
     
       8. The variable geometry turbine according to  claim 1 , wherein the projections cover portions from the leading edges or the trailing edges of the nozzle vanes to positions adjacent to the shafts, in a chord direction of the nozzle vanes.